This application is based on and incorporates herein by reference Japanese Patent Applications No. 2000-324393 filed Oct. 24, 2000 and No. 2001-48595 filed Feb. 23, 2001.
1. Field of the Invention
The present invention relates to an ignition system for internal combustion engines.
2. Related Art
An ignition system for internal combustion engines is designed to control the primary current flowing through the primary winding of an ignition coil to produce a high voltage at the primary current shut-off time, thereby generating a spark across the air gap of a spark plug. The primary current of the ignition coil is supplied from a d.c. power source (battery).
It is required to keep the ignition operation even in the event of failure of a component part or wiring of the ignition system so that the engine continues to run for the rimp-home performance. It is proposed for this performance to feed the primary current of the ignition coil from an additional separate d.c. power source in the event of system failure. This proposal is not so advantageous from the standpoint of installation space, maintenance and cost of the additional d.c. power source.
The present invention addresses this situation, and has its object to provide an ignition system for internal combustion engines which has a fail-safe function.
According to the present invention, a first switching device is turned on and off so that energy is stored in an energy storage coil and then the energy is released to charge a capacitor, and during an ignition period a second switching device is turned on and off so that the energy stored in the capacitor is released to the primary winding of an ignition coil to implement the ignition operation.
In the event of system failure, the second switching device feeds energy of a d.c. power source to the primary winding of an ignition coil by way of a reverse current blocking device, thereby enabling the rimp-home performance. In the normal state, the reverse current blocking device prevents the energy stored in the capacitor from flowing back to the d.c. power source.
In this manner, the ignition coil operates by being supplied with energy from the d.c. power source through the bypass at the occurrence of failure in the ignition current path, thereby enabling the rimp-home performance.